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Thread: totally confused over metric

  1. #1
    Boolit Master
    nekshot's Avatar
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    totally confused over metric

    Math was never my strong point in life but some of this metric stuff is confusing to me an ignorant old man! A 8mm mauser bore is .3106. Ok I get that. Now a 8.15x46 is bore .2992! I assumed this 8.15 would be the 8mm of .3106 plus 15. But according to the book a 8.15 is bore of .2992! I know they are right and I am confused. Any body willing to explain this to me? Go slow!
    Look twice, shoot once.

  2. #2
    Boolit Master
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    mm = .03937" usally round to .040" so 8mm .320"

  3. #3
    Boolit Master
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    Take a look at this thread, it might help ---
    http://castboolits.gunloads.com/show...x46R-Schuetzen


    Don

    What lies behind us and what lies before us are tiny matters compared to what lies within us.
    - Henry S. Haskins in “Meditations in Wall Street”

    "Political correctness is a doctrine, fostered by a delusional, illogical minority, and rapidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end." ...Unknown

  4. #4
    Boolit Master
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    That is a very inspirational thread but I still don't get the smaller diam. I know I am slow with this metric thing but I'm a trying! Reading of these guns sure puts the wants in me to have one. Rather than using the H&R single shot I think a Remington Russian single shot center fire rifle would have nice character. Would be an easy stub fit.
    Look twice, shoot once.

  5. #5
    Boolit Master
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    nekshot, were you taking measurements from a slugged bore as well as from a book?
    "In general, the art of government is to take as much money as possible from one class of citizens and give it to another class of citizens" Voltaire'

    The common virtue of capitalism is the sharing of equal opportunity. The common vice of socialism is the equal sharing of misery

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  6. #6
    Boolit Master GhostHawk's Avatar
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    When it comes to calibers there are no hard and fast rules IMO.

    Look at .44mag. How do you get .44 out of a .429 or .430 cast bullet?

    .38 special is another.

    People label stuff to suit themselves. And it gets stuck there.

  7. #7
    Boolit Master

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    Quote Originally Posted by GhostHawk View Post
    When it comes to calibers there are no hard and fast rules IMO.

    Look at .44mag. How do you get .44 out of a .429 or .430 cast bullet?

    .38 special is another.

    People label stuff to suit themselves. And it gets stuck there.
    And to add to the fun a 44 mag rifle has sammi specs to .432 what a mess

  8. #8
    Boolit Master
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    Quote Originally Posted by GhostHawk View Post
    When it comes to calibers there are no hard and fast rules IMO.

    Look at .44mag. How do you get .44 out of a .429 or .430 cast bullet?

    .38 special is another.

    People label stuff to suit themselves. And it gets stuck there.
    /\ THIS /\

    There's little uniformity in the naming of cartridges.
    English & metric designations for cartridges have little bearing on actual dimensions in the world of firearms.

  9. #9
    Boolit Master
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    The same way a 30 caliber wound up with a bullet of .308" diameter. There is only a general relationship between stated caliber and bullet diameter, or groove or bore diameter.

  10. #10
    Boolit Master Jedman's Avatar
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    Cartridges in 8 mm can vary over a wide range of diameters. Early 8 X 57 had .317 groove later .323 I have rifles in 8 X 56 and 8 X 50 that need .329-.330 diameter bullets.
    You were speaking of bore diameter and that varies wildly between different 8 mm cartridges also.

    Jedman

  11. #11
    Boolit Master
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    Way off topic, but I’ve heard that some of the old black powder loads (38, 44, 45) were named based on the diameter of the loaded case at the mouth. No idea if there is any truth to it.

  12. #12
    Boolit Master
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    I have a few 8mm rifles and my experience echo's Jedman's. I believe it was in 1913 the German government took it upon themselves to "Normalize" cartridge and bullet dimensions. WWI kinda got in the way and things didn't take off until after war. Even then it was slow going as there was so many variations of popular cartridges. If I remember correctly the 9.3 X 72R and the 8.15 X 46R were among the first to be Normalized. Probably because at that time they were among, if not the most popular cartridges. Even so, .318 barrels were still being used for a lot of the 8mm sporting rifle cartridges as they weren't going to waste them. I have a post WWI sporter with a .318 groove dia. barrel. The German military changed the groove diameter of the 8 X 57 from .318 to .323 in 1905 and I believe most military rifles then in service were tooled to that diameter. Later barrels were rifled to .323 groove dia. Bore diameter remained the same. By the beginning of WWII nearly all the popular, standard cartridges were Normalized. Rifles manufactured after WWII have been pretty standard.

    As several others have already said, there is no rhyme nor reason to the naming of cartridges and in the early years no standardization. Many early 9.3's, (.366), can easily, accurately and effectively shoot bullets of .358. I have been told by those who should know that a lot of the old German makers believed a tight bore was conducive to accuracy and, according to some of my rifles, they definitely were not afraid to do so!!!!
    "In general, the art of government is to take as much money as possible from one class of citizens and give it to another class of citizens" Voltaire'

    The common virtue of capitalism is the sharing of equal opportunity. The common vice of socialism is the equal sharing of misery

    NRA Benefactor 2008

  13. #13
    Boolit Master
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    Quote Originally Posted by sharps4590 View Post
    nekshot, were you taking measurements from a slugged bore as well as from a book?
    No, I am trying to educate myself what barrel I have that would also give the legit 8.15x46 name and what molds do I have that fit in that caliber. I was at first thinking this cartridge is close to .300 and would also give me reason to get 7.? carcano barrel. Then it seemed like I ran into information putting it around .321 and I like that as it can give company to the 32 winny. I would be happy if it was .318. Boy, can I confuse myself!
    Look twice, shoot once.

  14. #14
    Boolit Master Char-Gar's Avatar
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    Always remember Dear Ones, that the "bore" diameter and the "groove" diameter are different.
    Disclaimer: The above is not holy writ. It is just my opinion based on my experience and knowledge. Your mileage may vary.

  15. #15
    Boolit Master Texas by God's Avatar
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    My high school algebra teacher told me in 1974 that by 1980 the United States would be totally converted to the metric system. I told him I did not think so. I guess I won that argument!

    Sent from my SAMSUNG-SM-G930A using Tapatalk

  16. #16
    Boolit Master
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    Quote Originally Posted by Texas by God View Post
    My high school algebra teacher told me in 1974 that by 1980 the United States would be totally converted to the metric system. I told him I did not think so. I guess I won that argument!

    Sent from my SAMSUNG-SM-G930A using Tapatalk
    Unfortunately you did. Just think how simple it would be if we were totally metric. Changing from mm to cm to meters is just moving a decimal point. Remember, out money system is metric in nature.

  17. #17
    Boolit Master bdicki's Avatar
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    Quote Originally Posted by Texas by God View Post
    My high school algebra teacher told me in 1974 that by 1980 the United States would be totally converted to the metric system. I told him I did not think so. I guess I won that argument!

    Sent from my SAMSUNG-SM-G930A using Tapatalk
    The United States is moving to the metric system inch by inch.

  18. #18
    Boolit Master
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    Quote Originally Posted by bdicki View Post
    The United States is moving to the metric system inch by inch.
    Hahahahahaha!!!!!
    I see what you did there!!!

    What lies behind us and what lies before us are tiny matters compared to what lies within us.
    - Henry S. Haskins in “Meditations in Wall Street”

    "Political correctness is a doctrine, fostered by a delusional, illogical minority, and rapidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end." ...Unknown

  19. #19
    Boolit Man TRX's Avatar
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    Quote Originally Posted by KenH View Post
    Just think how simple it would be if we were totally metric.
    ...but a 7.62x54R, a 7.65x53 Mauser, and 7.7 Arisaka all shoot the same size bullet...

    Back in the day there were differences in sizes because some standards measured bore diameter, some the lands, and some the actual bullet.

    The name of a cartridge is just that; a name. Sometimes the name is chosen to make sure someone doesn't try to put the wrong cartridge in the wrong gun; .38 Colt Auto and .38 Super, or 9mm Largo and 9x23 Winchester, for examples. Sometimes "just because."

  20. #20
    Boolit Master Hick's Avatar
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    In its early form the 38 Special was a heeled bullet-- so it really was 0.38-- which matched the outside diameter of the case. As the cartridge evolved the brass stayed the same but the heeled bullets went out of use-- so we're left with a bullet that fits the inside of the case. So the name originally was really the size of the bullet, but the design changed later. Also, keep in mind that caliber often refers to the bore at the top of the lands. 30 caliber is 0.30 but the bullet has to be 0.308 to engrave in the rifling. Similarly, 0.303 British describes the bore, not the bullet. Of course, there is also the problem of describing a cartridge that fits the same bore as another one where you want to distinguish between them (for example-- all the different 30 caliber bullets). As noted in the posts above, this takes some imagination.
    Hick: Iron sights!

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